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Smarter Parental Controls

If you've been using the parental controls options in Mac OS X to lock your child out of using a particular computer late at night, but would like to employ a more clever technique to limit Internet access, turn to MAC address filtering on an Apple base station.

To do this, launch AirPort Utility, select your base station, and click Manual Setup. In the Access Control view, choose Time Access to turn on MAC filtering. You'll need to enter the MAC address of the particular computer, which (in 10.5 Leopard and 10.6 Snow Leopard) you can find in the Network System Preferences pane: click AirPort in the adapter list, and click Advanced. The AirPort ID is the MAC address.



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GIF Licensing Controversy

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In some circles, the term "Slashdot Effect" refers to the substantial increase in traffic a Web site receives after it is mentioned on Slashdot, a geek-oriented Web site (the name refers to the root directory on a Unix system, which can be specified as "/."). But we recently saw another kind of Slashdot Effect when one of the nerds who frequent the site spotted a vaguely worded document on Unisys's Web site indicating that the company is now offering LZW compression licenses to Web sites that use GIF images - for a flat rate of $5,000. LZW, or Lempel-Ziv-Welch, is a fast, efficient compression algorithm used in modems, disk controllers, hard disks, compression utilities, and tape drives. Unisys owns a patent on the LZW algorithm, and since the GIF file format employs LZW compression, any software that creates GIF files requires a license from Unisys. For coverage of the original licensing furor, see "The End of the GIF-Giving Season" in TidBITS-259.

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In short order, the Slashdot denizens - many of them free software advocates - had interpreted the release in the worst possible way, turning it into a Unisys plot to extort $5,000 from every site that contains GIF images, which would be pretty much all Web sites. A heated thread erupted to discuss the travesty, and a site, Burn All GIFs, appeared to combat the nefarious scheme by urging webmasters to show up at Unisys headquarters (on a day to be determined) and "burn their GIFs," however one is supposed to do that.


Belay Those Lighters! The GIF-burning is all smoke and no fire. A close reading of the Unisys announcement makes clear that you need a license "[i]f you use any of the types of images specified above on your Web site that you received from an unlicensed software developer or service." In other words, if the developer of the software being used to create the GIFs has a license, the site itself does not need one. All popular GIF tools, including Photoshop, DeBabelizer, ImageReady, Fireworks, and WebPainter, are properly licensed, so the impact on most users will be nil.

In point of fact, Unisys could not claim a patent on the GIF file format itself even if it wanted to - or for that matter on any file format that contains LZW-compressed data. The patent covers the LZW algorithm: the series of steps software (or an intrepid human being with pencil and paper) must perform to compress data using the technology. A GIF file, or any LZW-compressed data, does not embody the LZW algorithm itself, only the results of the algorithm. Only software can be in violation of a software patent. If Unisys attempted to sue a Web site operator merely for including LZW-compressed files on the site, the case would be thrown out of court; it's unsupportable under current U.S. law.

My reading of Unisys's announcement is that they want to make it easy for Web sites that use unlicensed LZW technology to "get legal." If your site uses GIF files created by a tool that does not have a valid LZW license from Unisys, paying the licensing fee will cover your liability, no matter what. It's unclear whether end users can be held responsible for using software that violates patents, but my guess is that this new license is aimed mostly at CGI programs, running on a Web server, that use freely available C libraries to output GIF files like real-time stock graphs.

At the time Unisys received its LZW patent, patents were good for 17 years from date of issue. This was later changed as part of the multi-national GATT (the General Agreement on Tariffs and Trade) to be 20 years from the date of first filing. That means Unisys's LZW patent will expire in mid-2003; under the old rules, it would have expired near the end of 2002 (there was a two year gap between the initial filing and the original patent being granted). Interestingly, according to a Free Software Foundation page explaining why the FSF site does not include GIFs, IBM applied for a patent on LZW at about the same time as Unisys - and because someone was asleep at the patent office, both IBM and Unisys received patents. IBM's runs out at about the same time as Unisys's. The FSF page also contains the interesting tidbit that the patent does not apply to software that only decodes LZW data, so all GIF display programs are free and clear. The page is a useful overview of the patent issues involved with LZW and GIF, albeit slanted toward Richard Stallman's slightly skewed (from the rest of us) point of view.


It seems unlikely in the extreme that Unisys will actually conduct a sweep of all Web sites to see who's using the company's patented technology without permission. There are simply too many sites, and it's impossible to tell what program created a GIF simply by examining the image (unless the software intentionally adds a comment tag providing such information). There is, in short, no way to enforce any requirement that Web sites obtain the offered license. So relax; the GIF Gestapo is not knocking on your door.

But many corporations have whole departments devoted to finding and correcting licensing issues (that is, illegal software) in the company. And most such companies have Web sites these days, many of which were built using software developed in-house. These companies may be willing to pay Unisys the $5,000 just to be safe. If only a hundred sites do, that's a cool half-million for Unisys - and all they had to do was move a press release. Not a bad increase in shareholder value for a day's work, which is, after all, what this flap is really about.

[Jerry Kindall is a freelance writer and contributing editor to MWJ, the Weekly Journal for Serious Macintosh Users, where this article was originally published. For more insightful Macintosh news, sign up for a free, no-obligation, three-issue trial subscription to MWJ at the journal's Web site. For more information on Jerry's work, visit the Web site of his company, Manual Labor.]



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